Engine cylinder valve control system

ABSTRACT

According to a control strategy, a cylinder valve control device is monitored and operation of the engine is modified. The cylinder valve control device includes a driving shaft driven by the engine to drive an intermediate member which in turn drives a cam arranged to open an engine intake valve, and a driver which is operative in response to a command to vary an amount of eccentricity of the intermediate member with respect to a shaft axis of the driving shaft. During one mode of engine operation, the intermediate member is supported in a support for rotation about an axis in eccentric condition with respect to the shaft axis to accelerate and decelerate the cam with respect to rotation of the driving shaft. During another mode of engine operation, the intermediate member is in concentric condition with respect to the shaft axis to provide a synchronous motion of the cam with rotation of the driving shaft. In response to the eccentricity of the intermediate member, the engine operation is modified.

This application is a Divisional of application Ser. No. 08/313,868,filed Sep. 28, 1994 now U.S. Pat. No. 5,592,908.

BACKGROUND OF THE INVENTION

The present invention relates to an engine cylinder valve control and asystem for controlling an internal combustion engine with such acylinder valve control device.

U.S. Pat. No. 3,633,555 discloses an engine cylinder valve controldevice for moving a cam relative to its driving shaft. This device isapplicable to an internal combustion engine to vary the movement of thecams which control the intake and/or exhaust valves of the engine. Thisknown device comprises a drive member rotatable with a driving shaft,and an intermediate member mounted in an external bearing which iseccentric with respect to the shaft. The shaft extends through anopening in the intermediate member dimensioned to allow limited movementof the bearing to vary the eccentricity. A cam is coaxial with the shaftand rotatable relative thereto. The device includes a first couplingbetween the drive member and the intermediate member at a first positionspaced from the shaft axis, and a second coupling between theintermediate member and the cam at a second position angularly spacedfrom the first position with respect to the shaft axis. The twocouplings are so spaced from the shaft axis that they are at varyingdistances from the axis of the intermediate member during operation.Each of these couplings has a movable connection with the intermediatemember to permit the variation in its distance from the axis of theintermediate member.

An object of the present invention is to improve a control strategy foran internal combustion engine with a cylinder valve control device suchthat information as to operation of the cylinder control device is usedin advantageous manner in controlling the engine.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, there is provided anengine cylinder valve control device for an internal combustion engine,comprising:

a driving shaft rotatable about a shaft axis;

a cam, adapted for actuating a cylinder valve, rotatable relative tosaid driving shaft;

a support;

an intermediate member supported in said support for rotation about anaxis;

a first coupling between said driving shaft said intermediate member ata first position spaced from said shaft axis;

a second coupling between said intermediate member and said cam at asecond position angularly spaced from said first position with respectto said shaft axis,

said first and second couplings being so spaced from said shaft axisthat they are at varying distances from said axis of said intermediatemember during operation, each of said first and second couplings havinga movable connection to permit the variation in its distances from saidaxis of said intermediate member;

a driver drivingly connected to said support for varying theeccentricity of said intermediate member,

a sensor arranged to detect an amount of the eccentricity of saidintermediate member and generate a sensor output representative of theamount of eccentricity;

means for generating a signal indicative of an engine speed of theinternal combustion engine;

means for controlling said driver, said controlling means beingoperative responsive to said sensor output and said engine speedindicative signal to modify operation of the internal combustion engine.

According to another aspect of the present invention, there is provideda method of controlling an internal combustion engine with a cylindervalve control device, the cylinder valve control device including adriving shaft driven by the engine to drive an intermediate member whichin turn drives a cam arranged to open an engine cylinder valve, and adriver which is operative in response to a command to vary an amount ofeccentricity of the intermediate member with respect to a shaft axis ofthe driving shaft, the intermediate member being supported in a supportfor rotation about an axis in eccentric condition to accelerate anddecelerate the cam with respect to rotation of the driving shaft duringengine operation, the intermediate member being in concentric conditionto provide a synchronous motion of the cam with rotation of the drivingshaft during engine operation, the method comprising the steps of:

providing an output distinguishing an operation of the intermediatemember in eccentric condition from an operation of the intermediatemember in concentric condition; and

suspending, responsive to said output, fuel supply to the internalcombustion engine upon the engine speed exceeding a predetermined enginespeed when said output represents the operation of the intermediatemember in eccentric condition.

According to still another aspect of the present invention, there isprovided a method of controlling an internal combustion engine with acylinder valve control device, the cylinder valve control deviceincluding a driving shaft driven by the engine to drive an intermediatemember which in turn drives a cam arranged to open an engine cylindervalve, and a driver which is operative in response to a command to varyan amount of eccentricity of the intermediate member with respect to ashaft axis of the driving shaft, the intermediate member being supportedin a support for rotation about an axis in eccentric condition toaccelerate and decelerate the cam with respect to rotation of thedriving shaft during engine operation, the intermediate member being inconcentric condition to provide a synchronous motion of the cam withrotation of the driving shaft during engine operation, the methodcomprising the steps of:

providing an output distinguishing an operation of the intermediatemember in eccentric condition from an operation of the intermediatemember in concentric condition;

suspending, responsive to said output, fuel supply to the internalcombustion engine upon the engine speed exceeding a first predeterminedengine speed when said output represents the operation of theintermediate member in eccentric condition; and

increasing, responsive to said output, fuel supply to the internalcombustion engine upon the engine speed dropping below a secondpredetermined engine speed that is lower than said first predeterminedengine speed and an amount of load imposed on the internal combustionengine being less than a predetermined engine load value when saidoutput represents the operation of said intermediate member inconcentric condition.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an engine control system with a cylindervalve control device;

FIG. 2 is a fragmentary top plan view of the cylinder valve controldevice;

FIG. 3 is a section taken through the line 3--3 in FIG. 2, showing theposition of parts when an intermediate member is in concentriccondition;

FIG. 4 is a longitudinal section taken through the line 4--4 in FIG. 3;

FIG. 5 is a cross section taken through the line 5--5 in FIG. 2;

FIG. 6 is a cross section taken through the line 6--6 in FIG. 2;

FIG. 7 is a similar view to FIG. 3, showing the position of parts whenthe intermediate member is in an eccentric condition;

FIG. 8(A) shows, in dotted curve, variation of deviation in phase of acam versus varying angle of a driving shaft when the intermediate memberis in the eccentric condition, and, in fully drawn line, no deviation inphase of the cam versus varying angle of the driving shaft when theintermediate member is in a concentric condition;

FIG. 8(B) shows, in dotted curve, a valve lift diagram when theintermediate member is in the eccentric condition, and, in fully drawnline, a valve lift diagram when the intermediate member is in concentriccondition;

FIG. 9, 10 and 11 are flow charts of a control strategy of the preferredimplementation of the present invention;

FIG. 12 is a flow chart alternative to the flow chart of FIG. 9;

FIG. 13 is a flow chart alternative to the flow chart of FIG. 9;

FIG. 14 is a graphical representation of an allowable upper limit ofengine speed versus varying amount of eccentricity of the intermediatemember;

FIG. 15 is a similar view to FIG. 3 showing a portion of a modifiedcylinder valve control device;

FIG. 16 is a hydraulic diagram;

FIGS. 17, 18 and 19 are flow charts of a modified portion of the controlstrategy; and

FIG. 20 is a similar view to FIG. 16 showing a modified hydraulicdiagram.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a system for controlling an internal combustion engine with acylinder valve control device 10 shown in FIGS. 2 through 6. Theinternal combustion engine is of the overhead camshaft type and has fourcylinders in this embodiment with two intake valves per each cylinder.The cylinder valve control device 10 is designed to actuate the intakevalves having tappets 12 and 14 (see FIG. 4).

Before explaining the engine controlling system shown in FIG. 1, thecylinder valve control device 10 is explained in connection with FIGS. 2through 6.

Instead of a single conventional camshaft, the control device 10 usesfour hollow double cams 16 arranged in line and rotatably supported bythe engine cylinder head via cam brackets 18 and 20. Extending throughall of the cams 16 is a driving shaft 22. The driving shaft 22 issupported within the cams 16 and rotatable about a shaft axis 24 byconventional means such as a toothed wheel and a chain. The drivingshaft 22 has fixed thereto four drive members or collars 26 which drivethe cams 16, respectively. As best seen in FIG. 4, the drive collar 26is fixedly coupled with the driving shaft 22 by means of a cotter 28 andhas a sleeve 30. The sleeve 30 has a reduced diameter end portion 32 fitinto the adjacent cam 16 and an annular shoulder 34 abutting theadjacent end of the cam 16. With the reduced diameter end portions 32 ofthe drive collars 26, the cams 16 are held in concentric relation withthe driving shaft 22 for relative rotation thereto about the shaft axis24. Mainly due to the annular shoulders 34, relative motion of the cams16 in the direction of the shaft axis 24 is restricted.

As shown in FIGS. 2, 4 and 6, the drive collar 26 is formed with aradial slot 36 slidably engaged by a first pin 38 of an intermediatemember in the form of an annular disc 40. The pin 38 is rotatablysupported by the annular disc 40 and projects from one face of the disc40 into the radial slot 36. Projecting from the opposite face of theannular disc 40 is a second pin 42 which is angularly spaced from thefirst pin 38 with respect to the shaft axis 24. In this embodiment, thesecond pin 42 is symmetrical to and angularly spaced through an angle of180 degrees to the first pin 38.

The annular disc 40 has a central hole 44 and is fitted around thedriving shaft 22 with ample radial clearance. The central hole 44 iswide so that the disc 40 does not touch the surface of the driving shaft22 and is free to move into positions eccentric with respect to thedriving shaft 22. The disc 40 is supported by a bearing 46 in a supportor disc housing 48 for rotation about an axis 50 (see FIGS. 3 and 7).The disc housing 48 is rotatably supported by a shaft 52 fixed to abracket mounted to the cylinder head and pivotal about an axis 54parallel to the shaft axis 24. The disc housing 48 is annular and has ahandle 56 angularly spaced from the shaft 52. Moving the handle 56 fromthe position shown in FIG. 7 to the position shown in FIG. 8 or viceversa causes the disc housing 48 and disc 40 to move in a planeperpendicular to the shaft axis 24.

The second pin 42 is rotatably supported by the disc 40 and slidablyengages a radial slot 58 in a driven member or collar 60, forming anintegral part and thus rotatable with the adjacent cam 16. The cam 16has two cam lobes 62 and 64 for the tappets 12 and 14 of the cylindervalves.

As best seen in FIG. 3, the cylinder valve is of the poppet type havingthe tappet 12 and a stem portion 70. The cylinder valve is biased to avalve closed position by a spring 74 which reacts between the cylinderhead structure (not shown) and a spring retainer 76.

Referring to FIG. 3, the support or disc housing 46 is moved by a driver80. The driver 80 includes a motor in the form of a stepper motor 82having a rotary output shaft 84. Rotary motion of the output shaft 84 isconverted into linear motion of a non-rotative nut 86 by means of abevel gear 88 fixed to the output shaft 84, a mating bevel gear 90 fixedto a power screw 92 which is threadedly engaged with the nut 86. The nut86 has a mouth 94 receiving the handle 56 and a clearance adjustor 96 tohold the handle 56 in the mouth 94. The screw 92 is rotatably supportedby a portion 98 of the engine cylinder head and a bracket 100 fixed tothe engine cylinder head. As shown in FIG. 2, the nut 86 isnon-rotatively supported by a guide 102 for a linear motion.

The stepper motor 82 is operatively coupled with an engine control unit104 (see FIG. 1) via a line 106. The control unit 104 is operative toprovide a concentric command or an eccentric command to the driver 80.

During engine operation at high speeds, the control unit 104 providesthe concentric command to the stepper motor 82 and the driver 80conditions the intermediate member or annular disc 40 in concentriccondition with respect to the shaft axis 24. In other words, the supportor disc housing 48 assumes the position shown in FIG. 3 wherein the axis50 of the annular disc 40 agrees completely with the shaft axis 24 andloses its identity. Rotation of the cam 16 with two cam lobes 62 and 64actuates the intake valves. The valve lift diagram, which is determinedby the profile of the cam lobes 62 and 64, is illustrated by the fullydrawn curve in FIG. 8(B). It is noted that, in concentric condition, theannular disc 40 provides a synchronous motion of the cam 16 withrotation of the driving shaft 22.

During engine operation at low speeds, the control unit 104 provides theeccentric command to the stepper motor 82. Upon a change in command fromthe concentric command to the eccentric command and vice versa, thestepper motor 82 turns the rotary output shaft 84, causing the nut 86 tomove from the position shown in FIG. 3 to the position shown in FIG. 7and vice versa.

At the position shown in FIG. 7, the disc housing 48 produces aneccentricity or an offset between the axis 50 of the annular disc 40 andthe shaft axis 24. In other words, the intermediate member or annulardisc 40 is in eccentric condition with respect to the shaft axis 24.Under this condition, the cam 16 is driven faster than the rotationalspeed of the driving shaft 22 over one part of the driving shaftrevolution and then driven slower than the rotational speed of thedriving shaft 22 over another part of the same revolution. The dottedline curve of FIG. 8A shows that the phase of the cam 16 advances overone part of the driving shaft revolution and then retards over anotherpart of the same revolution. The dotted line curve in FIG. 8B shows avalve lift diagram of the intake valve in eccentric condition, while thefully drawn curve shows a valve lift diagram of the intake valve inconcentric condition. Comparing the valve lift diagrams in FIG. 8B, itis seen that the valve opening duration in eccentric condition becomesshorter than the valve opening duration in concentric condition. This isbecause the annular disc 40 rotates about the axis 50 in eccentriccondition to accelerate and decelerate the cam 16 with respect torotation of the driving shaft 22.

Referring back to FIG. 1, the control unit 104 is further described. Thecylinder valve control device 10 is fitted to actuate intake valves 108of the internal combustion engine having exhaust valves 110, spark plugs112 and fuel injectors 114. Intake air is supplied to the intake valves108 via an air clearner 116 past a throttle chamber 118 containing athrottle valve 120.

The control unit 104 is operative to determine and provides a fuelinjection pulse to the fuel injectors 114 in response to informationderived from a crank angle sensor 122, an air flow meter 124, a coolanttemperature sensor 126, an oxygen (O₂) sensor 128, a throttle sensor 130and a vehicle speed sensor 132. The crank angle sensor 122 is driven byan exhaust camshaft to detect a 1 degree signal and a 120 degrees signaland sends them to the control unit 104. The air flow meter 124 is of thehot wire type and outputs a voltage signal proportional to the air flowrate. The coolant temperature sensor 126 is mounted to detecttemperature of engine coolant flowing adjacent the engine intakemanifold and provides resistance which varies with coolant temperature.The O₂ sensor 128 is mounted to the engine exhaust manifold to provideoutput representative of oxygen concentration in the engine exhaustgases. The throttle sensor 130 is combined with a throttle switch havingidle contacts. The vehicle speed sensor 132 provides pulse signalsgenerated via a speed meter 134 to the control unit 104. The abovementioned sensors and meter 122, 124, 126, 128, 130 and 132 and themanner of determining the fuel injection pulse are described in ServiceManual (C34-1) entitled "NISSAN LAUREL, INTRODUCTION TO MODEL OF THE C34TYPE" published in January, 1993 by Nissan Motor Co. Ltd. Particularattention is paid to description and illustration related to a doubleoverhead cam (DOHC) electronic fuel injection (EGI) engine of the RB25DEtype on pages B-60 to B-64 of this Service Manual and to systemcomponents on pages B-76 to B-79 thereof.

Simply explaining, an amount of fuel injection Ti can be expressed bythe following equation:

    Ti=2×Te+Ts                                           Eq 1

where: Te represents an effective amount of fuel injection; and

Ts represents an amount for compensating for a delay of fuel injectorowing to a drop in output voltage of vehicle battery.

The effective amount of fuel injection Te can be expressed by thefollowing equation:

    Te=Tp×ALPHA×K×Co                         Eq 2

where: Tp represents a basic amount of fuel injection which isdetermined in response to intake air flow rate and engine speed detectedby the air flow meter 124 and crank angle sensor 122;

ALPHA represents a coefficient for air fuel ratio feedback;

K represents a coefficient derived from air fuel ratio learning; and

Co represents various correction coefficients.

The control unit 104 is operative to perform a so-called "idle speedcontrol" wherein, when the throttle valve is fully closed, the intakeair is controlled by an auxiliary air control (AAC) valve 136 and an airregulator 138 in response to engine warming-up conditions and engineoperating conditions. For this control, the control unit 104 receivesinformations from the crank angle sensor 122, coolant temperature sensor126, throttle sensor 130 and vehicle speed sensor 132. The control unit104 receives information from a neutral switch 140 mounted to anautomatic transmission 142 driven by the engine. The AAC valve 136 andair regulator 138 are provided to control an auxiliary air bypassing thethrottle valve 120. The air regulator 138 is of the bimetal type and hasa heater to add heat to the auxiliary air upon supply of electriccurrent. The supply of electric current is interrupted by the bimetalswitch when the coolant temperature exceeds a predetermined value. TheAAC valve 136 is a solenoid valve directly operated by the output of thecontrol unit 104. This valve 136 is actuated in ON-OFF manner. The flowrate of auxiliary intake air is proportional to a ratio of ON durationto one cycle duration. The control unit 104 can vary this ON duration tocontrol the flow rate of auxiliary intake air. The above mentioned AACvalve 136 and air regulator 138 and the manner of performing the idlespeed control are described in the above-mentioned Service Manual(C34-1) entitled "NISSAN LAUREL, INTRODUCTION TO MODEL OF THE C34 TYPE."Particular attention is paid to description and illustration on pagesB-67 and B-68 and pages B-80 and B-81 of the Service Manual.

Simply explaining, the control unit 104 effects a feedback controlwherein the AAC valve 136 is operated to keep engine speed within acalibrated window around a target engine idle speed. This feedbackcontrol is initiated when the following first and second conditions aremet and terminated when at least one of them fails to be met.

First Condition . . . the control unit 104 determines that the idlecontacts of the throttle sensor 130 are closed;

Second Condition . . . the control unit 104 determines that the vehiclespeed is below a predetermined speed, e.g., 8 km/h or the neutral switch140 is turned "ON."

The control unit 104 is operative to determine whether the intermediatemember or annular disc 40 is in eccentric condition or in concentriccondition in response to information provided by a sensor in the form ofa potentio meter 144 shown in block diagram in FIG. 2. The potentiometer 144 is arranged to detect a position taken by the rotary outputshaft 84 and provides a position signal indicative of the detectedposition to the control unit 104. It is seen that the detected positionrepresents an amount of eccentricity of the annular disc 40. Thus, it isconsidered that the potentio meter 144 detects the amount ofeccentricity of the annular disc 40 and its sensor output in the form ofthe position signal is representative of the detected amount ofeccentricity.

The flow charts of FIGS. 9, 10 and 11 illustrate a control strategy ofthe preferred implementation of the present invention. Execution of thecontrol routine of FIG. 9 is repeated at regular intervals. At an inputblock 150, the control unit 104 inputs information of engine speed RPM,throttle valve position TH and output shaft 84 position POS based on theoutputs of the crank angle sensor 122, throttle sensor 130 and potentiometer 144.

In a box 152, the control unit 104 determines whether POS is greaterthan or equal to a predetermined value R. If POS is greater than orequal to R, the control unit 104 determines that the annular disc 40operated in eccentric condition, while if POS is less than R, itdetermines that the annular disc 40 operates in concentric condition.

If POS is greater than or equal to R in box 152, the control logic goesto a box 154 where the control unit 104 determines whether RPM isgreater than a first predetermined engine speed of 5000, i.e., 5000 rpm.If RPM is less than or equal to 5000, the control unit 104 resets a flagF/C in a box 156. Then, the control logic returns to a point of START.If RPM is greater than 5000 in box 154, the control unit 104 sets theflag F/C in a box 158 before the control logic returns to the point ofSTART.

In box 152, if POS is less than R, the control logic goes to a box 160where the control unit 104 determines whether RPM is less than a secondpredetermined engine speed of 1500, i.e., 1500 rpm. If RPM is greaterthan or equal to 1500, the control unit 104 resets a flag F/U in a box162. Then, the control logic returns to the point of START. If, in box160, RPM is less than 1500, the control unit 104 determines, in a box164, whether TH is less than a predetermined throttle position θ_(T). IfTH is greater than or equal to θ_(T), the control logic goes to the box162. If TH is less than θ_(T) in box 164, the control logic goes to abox 166 where the control unit 104 sets the flag F/U before returning tothe point of START.

Execution of the flow chart of FIG. 10 is repeated at regular intervals.This simplified flow chart is intended to show in what manner thecontrol unit 104 suspends fuel supply to the engine. In a box 170, thecontrol unit 104 determines whether the flag F/C is set. If F/C is notset, the control logic goes to a block 172 where the control unit 104determines whether predetermined fuel-cut entry conditions are met. Ifthe fuel-cut entry conditions are met, the control logic goes to a box174 where the control unit 104 issues a command for suspending fuelsupply to the engine. If, in box 172, the fuel-cut entry conditions arenot met, the control logic goes to a box 176 where the control unit 104determines whether predetermined recovery conditions are met. If thepredetermined recovery conditions are not met, the control logic goes tobox 174. If, in box 176, the predetermined recovery conditions are met,the control logic goes to a box 178 where the control unit 104 issues acommand for resuming supply of fuel to the engine.

In box 170, if the flag F/C is set, the control logic goes to box 174and the control unit 104 issues the command for suspending fuel supplyto the engine. The control logic returns to a point of START of thisroutine after box 174 or box 178.

The predetermined fuel-cut entry conditions and recovery conditions aredescribed on pages B-63 and B-64 of the before-mentioned Service Manual(C34-1) entitled "NISSAN LAUREL, INTRODUCTION TO MODEL OF THE C34 TYPE."

From the preceding description along with the flow charts of FIGS. 9 and10, it is seen that the control unit 104 is operative to suspend fuelsupply to the engine upon the engine speed RPM exceeding thepredetermined engine speed of 5000 rpm when the annular disc 40 operatesin eccentric condition. It is readily appreciated that according to thiscontrol strategy, the engine speed is always held lower than anallowable upper limit for operation of the cylinder valve control device10 with the annular disc 40 in eccentric condition.

Execution of the flow chart of FIG. 11 is repeated at regular intervals.At a box 180, the control unit 104 determines the basic fuel amount Tpby, for example, performing a table look-up operation. Then, the controllogic goes to a block 182 where the control unit 104 determines whetherthe flag F/U is set. If, the flag F/U is not set, the control logic goesto a box 184 where the control unit 104 determines the amount of fuelinjection Ti using the equation Eq 1. In a box 186, the control unit 104outputs fuel injection pulse having a duration representing the amountTi to the fuel injectors 114.

If, at box 182, the flag F/U is set, the control logic goes to a box 188where the control unit 104 increases Tp by a unit amount delta Tp beforethe control logic goes to box 184. In this case, the increased amount offuel injection Ti is supplied to the engine by the fuel injectors 114.The control logic returns to a point of START of this routine after box186.

From the preceding description along with the flow charts of FIGS. 9 and11, it is seen that the control unit 104 is operative to increase fuelsupply to the engine upon the engine speed RPM dropping below the secondpredetermined engine speed of 1500 rpm and the throttle position THbeing less than the predetermined throttle position θ_(T) when theannular disc 40 operates in concentric condition. It is readilyappreciated that according to this control strategy, the engine speed isalways held higher than an allowable lower limit for operation of thecylinder valve control device 10 with the annular disc 40 in concentriccondition.

The flow chart of FIG. 9 may be replaced with an alternative flow chartof FIG. 12. In FIG. 12, after an input box 150, the logic flow goes to abox 190 where the control unit 104 determines whether RPM is greaterthan the first predetermined engine speed of 5000, i.e., 5000 rpm. IfRPM is greater than 5000, the control logic goes to a box 192 where thecontrol unit 104 determines whether POS is greater than or equal to thepredetermined value R. If POS is greater than or equal to R, the controlunit 104 determines that the annular disc 40 operates in eccentriccondition. If POS is less than R, the control unit 104 determines thatthe annular disc 40 operates in concentric condition.

If, in box 192, POS is less than R, the control logic goes to a box 194where the control unit 104 resets flag F/C before returning to a pointof START. If, in box 192, POS is greater than or equal to R, the controllogic goes to a box 196 where the control unit 104 sets flag F/C beforereturning to the point of START.

If, in box 190, RPM is less than 5000, the control logic goes to a box198 where the control unit 104 determines whether RPM is less than asecond predetermined engine speed of 1500, i.e., 1500 rpm. If POS isless than 1500, the control logic goes to a box 200 where the controlunit 104 determines whether POS is greater than or equal to R. If POS isgreater than or equal to R, the control logic goes to a box 202 whereflag E/U is reset. If POS is less than R, the control logic goes to abox 204 where the control unit 104 determines whether TH is less than apredetermined engine load value of θ_(T). If TH is greater than or equalto θ_(T), the control logic goes to box 202 before returning to thepoint of START. If TH is less than θ_(T), the control logic goes to box206 where the control unit 104 sets flag E/U before returning to thepoint of START. If, in box 198, RPM is greater than or equal to 1500,the control logic goes to the box 202 where flag E/U is reset beforereturning to the point of START.

FIG. 13 shows another alternative to the flow chart of FIG. 9. The flowchart of FIG. 13 is substantially the same as the flow chart of FIG. 9except the addition of a box 210 disposed downstream of the box 152 andthe addition of a box 212 in place of the box 154. FIG. 14 shows, in thefully drawn line, a set of values for the first predetermined enginespeed. In FIG. 14, the vertical axis represents the first predeterminedengine speed indicated by MAX, while the horizontal axis representseccentricity indicated by POS, i.e., the output of the potentio meter144. The fully drawn line is indicated by F(POS). These engine speedvalues are set slightly below allowable engine speed values foroperation of the annular disc 40 in varying eccentric conditions. Itwill be noted from FIG. 14 that the predetermined engine speed valuedrops in accordance with increasing eccentricity of the annular disc 40.

At box 210 in FIG. 13, the control unit 104 determines the firstpredetermined value MAX by performing a table look-up operation of FIG.14 using POS. Then, the control logic goes to box 212 where the controlunit 104 determines whether RPM is greater than MAX. If RPM is greaterthan MAX, the control logic goes to box 158 where flag F/C is set,while, if RPM is equal to or less than MAX the control logic goes to box156 where the control unit 104 resets flag F/C.

In the preceding description, the support or disc housing 46 is moved bythe driver 80 including the stepper motor 80, and the sensor in the formof the potentio meter 144 provides information to the control unit 104.The disc housing 46 can be moved by hydraulic means as shown in FIGS. 15and 16. In FIG. 15, the sensor is in the form of a limit switch 220.

In FIG. 15, the position of parts when an intermediate member or annulardisc 40 operates in concentric condition is fully drawn, while theposition of parts when the annular disc 40 is in eccentric condition isdrawn by dotted line. The limit switch 220 is arranged such that it isnormally turned OFF, but it is turned ON by engagement with a support ordisc housing 48 when the annular disc 40 is in eccentric condition.

The hydraulic means includes a hydraulic piston 222 opposed to a springbiased piston 224 which is biased by a spring 226 to hold a handle 56 ofthe disc housing 48 in contact with the hydraulic piston 222. When thereis no supply of hydraulic fluid to a piston chamber 228, the hydraulicpiston 222 assumes a retracted position shown in FIGS. 15 and 16 owingto the bias of the spring 226, holding the disc housing 48 and thusannular disc 40 in concentric condition. The hydraulic piston 222assumes a projected position in response to supply of hydraulic fluid tothe piston chamber 228 against the bias of the spring 226, holding thedisc housing 48 and the annular disc 40 in eccentric condition andturning the limit switch 220 ON. The supply of hydraulic fluid to anddischarge thereof from the piston chamber 228 is conducted by atwo-position solenoid valve 230 having a solenoid 232 and a spring 234.Energization or deenergization of the solenoid 232 is responsive tooutput of a control unit 104. The solenoid valve 230 has a spring setposition as illustrated at 236 and a solenoid set position asillustrated at 238. Upon deenergization of the solenoid 232, the springset position 236 is established. In this position 236, hydraulic fluidis discharged from the piston chamber 228. Upon energization of thesolenoid 232, the solenoid set position 238 is established. In thisposition 238, hydraulic fluid from a pump 240 is supplied to the pistonchamber 228. The control strategy is as follows: In response to aconcentric command issued by the control unit 104, no electic current issupplied to the solenoid 232 to render same deenergized (OFF) andhydraulic fluid is discharged from the piston chamber 228, allowing thespring 226 to hold the annular disc 40 in concentric condition. Inresponse to an eccentric command, electric current is supplied to thesolenoid 232 to render same energized (ON) and hydraulic fluid issupplied to the piston chamber 228, urging the hydraulic piston 222 tomove the disc housing 48 against the spring 234 to the position asillustrated by the one-dot chain line in FIG. 16 where the annular disc40 is in eccentric condition. FIGS. 17, 18 and 19 show flow chartsalternative to the flow chart of FIG. 9. The flow charts of FIGS. 17 to19 illustrate a modified portion of the control strategy of thepreferred implementation of the present invention. This modification isneeded to fit the control strategy to the driver in the form ofhydraulic means illustrated in FIGS. 15 and 16.

Execution of the control routine of FIG. 17 is repeated at regularintervals. At a box 250, the control unit 104 fetches the presentcommand COM. At a box 252, the control unit 104 determines whether thepreviously stored old command COM_(OLD) is equal to the present commandCOM. If the present command COM is equal to the old command COM_(OLD)and thus there is no change in command, the control logic goes to a box254 where the control unit 104 moves the content of the present commandCOM to the old command COM_(OLD). Then, the control logic returns to apoint of START.

If there is a change in command, i.e., a change from the eccentriccommand to the concentric command or vice versa, an answer to theinterrogation at box 252 is negative and the logic flow goes to a box256 where the control unit 104 moves the content of the present commandCOM to the old command COM_(OLD). Then, the logic flow goes to a box 258where the content of a timer T of a timer routine is reset to initiatecounting of time by the timer routine. At a box 260, the control unit104 fetches the content of the timer T. At a box 262, the control unit104 determines whether the content of timer T is greater than apredetermined period of time of 0.1 second. An answer to theinterrogation at box 262 is negative until the content of the timer Texceeds the predetermined period of time. Setting of this predeterminedperiod of time is made in due consideration of a delay between themoment of occurrence of the change in command and the momenmt ofcompletion of a shift between the concentric position and the eccentricposition of the disc housing 48. When the counted time T has reached thepredetermined period of time, the logic flow goes from box 262 to a box264 where the control unit 104 checks the present command COM anddetermines whether the present command COM is the concentric command. Ifthe present command COM is the concentric command, the logic flow goesto a box 266 where the control unit 104 determines whether the limitswitch 220 is turned ON. If the limit switch 220 is turned ON, the logicflow goes to a box 268. In box 268, the control unit 104 sets a flag F1and records that a shift to an operation in concentric condition hasfailed. After box 268 the logic flow returns to the point of START. If,at box 266, the limit switch 220 is turned OFF, the logic flow goes to abox 270 where the control unit 104 resets the flag F1 before returningto the point of START.

If, at box 264, the present command COM is eccentric command, the logicflow goes to a box 272 where the control unit 104 determines whether thelimit switch 220 is turned ON. If the limit switch 222 is turned OFF,the logic flow goes to a box 274 where the control unit 104 sets a flagF2 and records that a shift to an operation in eccentric condtion hasfailed. After box 274 the logic flow returns to the point of START. If,at box 272, the limit switch 220 is turned ON, the logic flow goes to abox 276 where the control unit 104 resets the flag F2 before returningto the point of START.

Referring to the control routine of FIG. 18, at a box 280, the controlunit 104 determines whether flag F1 is set. If flag F1 is not set, thelogic flow goes to a box 282 where the control unit 104 resets flag F/Cbefore returning to a point of START. If flag F1 is set, the logic flowgoes to a box 284 where the control unit 104 determines the engine speedRPM based on information from the crank angle sensor 122. At a box 286,the control unit 104 determines whether RPM is greater than the firstpredetermined engine speed of 5000 rpm. If RPM is equal to or less than5000 rpm, the control logic goes to box 282. If RPM is greater than 5000rpm, the control logic goes to a box 288 where the control unit 104 setsflag F/C before returning to the point of START.

Referring to the control routine of FIG. 19, at a box 290, the controlunit 104 determines whether flag F2 is set. If flag F2 is not set, thelogic flow goes to a box 292 where the control unit 104 resets flag F/Ubefore returning to a point of START. If flag F2 is set, the logic flowgoes to a box 294 where the control unit 104 determines the engine speedRPM based on information from the crank angle sensor 122 and determinesthe throttle valve position based on information from the throttlesensor 130. At a box 296, the control unit 104 determines whether RPM isless than the second predetermined engine speed of 1500 rpm. If RPM isgreater than or equal to 1500 rpm, the logic flow goes to box 292. IfRPM is less than 1500 rpm, the logic flow goes to a box 298 where thecontrol unit 104 determines whether TH is less than the predeterminedengine load θ_(T). If TH is greater than or equal to θ_(T), the logicflow goes to box 292. If TH is less than θ_(T), the logic flow goes to abox 300 where the control unit 104 sets flag F/U before returing to thepoint of START.

FIG. 20 is an alternative to the hydraulic means shown in FIG. 16. Thehydraulic means of FIG. 20 is different from that of FIG. 16 in that,when there is no supply to a piston chamber 228, a spring 226 holds ahandle 56 to a position corresponding to operation of an annular disc 40in eccentric condition, and when there is supply of hydraulic fluid tothe piston chamber 228, a hydraulic piston 222 holds the handle 56 to aposition corresponding to operation of the annular disc 40 in concentriccondition.

What is claimed is:
 1. A method of controlling an internal combustionengine with a cylinder valve control device including a driver which isoperative in response to a first command to condition the cylinder valvecontrol device to open a cylinder valve suitable for engine operation atlow speeds, the driver being operative in response to a second commandto condition the cylinder valve control device to open the cylindervalve suitable for engine operation at high speeds, the methodcomprising the steps of:providing an output distinguishing an operationof the cylinder valve control device conditioned to open the cylindervalve suitable for engine operation at low speeds from an operation ofthe cylinder valve control device conditioned to open the cylinder valvesuitable for engine operation at high speeds; and suspending, responsiveto said output, fuel supply to the internal combustion engine upon theengine speed exceeding a predetermined engine speed when said outputrepresents the operation of the cylinder valve control deviceconditioned to open the cylinder valve suitable for engine operation atlow speeds.
 2. A system for controlling an internal combustion enginehaving a cylinder valve, the internal combustion engine being operableon fuel supplied thereto, comprising:a driving shaft rotatable about ashaft axes; a cam arranged to actuate the cylinder valve, said cam beingrotatable relative to said driving shaft; a support; a drive memberbetween said driving shaft and an intermediate member, said drive memberbeing rotatable with said driving shaft and coupled with saidintermediate member at a first position spaced from said shaft axis; adriven member between said intermediate member and said cam, said drivenmember being rotatable with said cam and coupled with said intermediatemember at a second position angularly spaced from said first positionwith respect to said shaft axis; said first and said second positionbeing so spaced from said shaft axis that they are at varying distancesfrom a central axis of said intermediate member during operation, eachof said drive and said driven members having a movable connection withsaid intermediate member to permit a variation in its respectivedistance from said central axis of said intermediate member; a driverdrivingly connected to said support to position said support toestablish an eccentric position so that there is an offset between saidcentral axis of said intermediate member and said shaft axis in responseto an eccentric command, and to position said support to establish aconcentric position so that there is alignment between said central axisof said intermediate member and said shaft axis in response to aconcentric command; an intermediate member condition detecting sensorarranged to detect said offset between said central axis of saidintermediate member and said shaft axis and generate an offset signalindicative of the detected offset; an engine speed detecting sensorarranged to detect an engine speed of the internal combustion engine andgenerate an engine speed signal indicative of the detected engine speed;and a control unit operatively coupled with said sensors and saiddriver, said control unit being operative to compare said offset signalwith a predetermined offset value and provide a first signal when saidoffset signal is greater than said predetermined offset value, saidcontrol unit being operative to compare said engine speed signal with apredetermined engine speed value and provide a second signal when saidengine speed signal is greater than said predetermined engine speedvalue, said control unit being operative to suspend fuel supply to theinternal combustion engine when both said first signal and said secondsignal are present.